As printing technology becomes more sophisticated and printers more capable of producing text and graphics with quality that is acceptable for almost any intended application, printers are becoming more available to all computer users. The most popular printer for its ease of use and quiet, dependable operation is the laser-type electrostatic printer, which produces a superior print quality and is faster and quieter than printer types that predate it, such as the dot matrix, daisy wheel, thermal, and ink-jet. For purposes of this specification printers that write on a drum by LED or LCD instead of a laser, and use a fuser-heater to fuse toner to the paper, are included as laser-type printers.
The laser-type printer uses a mechanism similar to that of a photocopy machine. The image is written on a photosensitive drum by a laser in the case of a laser printer. In other printers the image is written by an LED bar or an LCD shutter. Toner is attracted to the areas on the drum that have been written. The toner is then heated by the fuser-heater to fuse it to the paper to produce the printout. Because laser-type printers print an entire page at a time and the drum may be scanned quickly, they are much faster than most other printer types. Typically such a printer has an electronic buffer that can store a page or several pages of data depending on the amount of memory it has available for use. In a network comprising several computers and printers, printer buffers are inclined to be rather large and a network server, if present, usually means that a more than adequate amount of memory is available. A print request sent by a computer is received by the printer buffer and scheduled for printing, which typically commences when the buffer contains a full page and a "not busy" message is received from the printer. The process of printing is one of processing pages sent by the computer to the printer that are held in the printer's buffer. If the amount of material being sent to the printer is greater than the size of the buffer, the host computer is forced to hold until the buffer is cleared and can again accept print input, and so on until all pages are printed.
In a typical working environment, the printers are left on all the time as a convenience to users and are consequently consuming power in order to keep the fuser-heater at the proper operating temperature and the printer ready to print in response to instructions from a connected computer, i.e. a print request. The fuser-heater is the principal consumer of power in a laser-type printer and typically a fan for dissipating heat from the fuser-heater is the main source of noise. If a printer is allowed to run continually and no printing instructions are received, the fuser-heater will be kept at a certain set temperature, the fan will continue to operate to cool the rest of the printer, and the printer will be in a ready state. If the printer is turned off when not being used, it will require a certain amount of time to bring the fuser-heater up to a proper temperature and begin carrying out instructions from the computer when it is turned on again in response to a print command. The amount of time required for a fuser-heater to reach operating temperature is dependent on several factors that are unique to each printer. The wait that is necessarily involved is awkward and costly in a multi-user environment.
With several computers and one or more printers running in an enclosed area, there may be a heat build-up that must be eliminated through climate control equipment to maintain a successful operation. If the principle heat-producing element in a laser-type printer, the fuser-heater, could be turned off for times of non-use, this problem would be considerably reduced.
What is clearly needed is an automatic management system for shutting down a printer fuser-heater during periods of inactivity without disrupting operations, and that is compatible with existing systems.